On Tue, 17 Mar 98 03:18:37 -0800 Rich Measures <measures@vc.net> writes:
>
>Only in relation to defective anode cooler welds, not to bent filament
>
>helixes.
The welds caused infant mortality. The long term problem was real gas,
not the vanishing kind. I had several bad ones sent to me and they all
had that telltale glow...or worse. I was only able to recover one out of
maybe a dozen.
>>I can only relate a few of the hooror stories of the hams that
>>bought '89 tubes for spares only to have them go bang when used
>several
>>years later.
>>Actually I commend your honesty about the date code Rich...others
>would
>>have tried to hide it.
>>
>By what mechanism does an allegedly defective tube damage the
>parasitic
>suppressor R and blow the grid choke?
A big bang in an amp without a HV surge resistor.
>>I was buying 3-500Z's at 100 a time from Eimac then and even right
>out of
>>the box I had a high failure rate. It was around 1992 or so that I
>really
>>got feedback from those ...many good friends...that had decided to
>use
>>their "spares". and having big bangs.
>>It was also at that time that I started a serious evaluation of all
>the
>>Chinese versions. Today...1998 I only buy Chinese. Failures are
>>virtually zero..
>>
>>Rich..and others ..it is my "opinion only"...that a huge majority of
>>Eimac 3-500Z failures are due ONLY to poor quality tubes...NOTHING
>ELSE.
>>I fail to see any failures with Amperex (1968 and later) or good
>Chinese
>>(1994 and later) versions that even approximate the Eimac
>experiences. I
>>stress the word ANY.
>>
>I have tested Amperex and Chinese [Penta] tubes that failed from a
>bent
>filament helix.
>
>>I suspect that I know the source of those tubes and amp which is why
>I
>>asked.
>>
>The two, new tubes came with the new TL-922.
>>
>>Bang..yes...parasitic..highly doubtful.
>>
>Only if you can explain a plausible alternative scenario based on the
>circumstantial evidence. . Your serve, Carl.
Real proof would clinch it Rich. How about setting up a SB-220, TL-922,
etc with a spectrum analyzer and try to create the incident ?
Until that occurs I find it a real stretch to believe that a brand new 9
year old amp and tubes would harbor a dreaded parasitic at turn-on.
73 Carl KM1H
>cheers
>Rich...
>
>R. L. Measures, 805-386-3734, AG6K
>
>
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>
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